Setting D/T on primary

I am having a little problem trying to decide how to properly set the primary D/T on a P/S plumbed boiler. I replaced the primary pump on the Alpine 80 with a Taco Bumblebee as the pump curve showed it matched very closely what I was looking for. I wanted to get a 35* D/T across the boiler so as to maximize efficiency. The bumblebee's flow indicator is WAY off. It should be in the range of 4.2GPM when set the constant speed #2, which it is. The flow indicates 9.8GPM. My confusion comes from how to set the primary D/T when set to high fire in reguards to the zones. Should all zones be running or not?

I am having a little problem trying to decide how to properly set the primary D/T on a P/S plumbed boiler. I replaced the primary pump on the Alpine 80 with a Taco Bumblebee as the pump curve showed it matched very closely what I was looking for. I wanted to get a 35* D/T across the boiler so as to maximize efficiency. The bumblebee's flow indicator is WAY off. It should be in the range of 4.2GPM when set the constant speed #2, which it is. The flow indicates 9.8GPM. My confusion comes from how to set the primary D/T when set to high fire in reguards to the zones. Should all zones be running or not?

Thanks,

Tom

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To the best of my knowledge bumble bee calculates indicated gpm and does not measure it. I had same problem, and now do not even pay attention to gpm indication. Why did you set bumble bee to constant speed. Set it up to delta T.

Thanks for the reply and sorry for getting back so late, been busy with other projects and company.

I decided to use constant speed initally as I wanted to make sure the D/T would work and not ruin the HE in the boiler.
I have two of the pumps and use the other on another zone. I found that it is quite slow to respond to temp changes when monitoted with a digital meter.

It has time constant , to react slowly, because it was designed for heating zone, so as it reads return temperature, there is certain time needed for the water to move trough the heating piping. But it should work fine on boiler circuit. Also , because of wider delta t flow trough boiler is decreased. I would set higher temperature on reset curve, if you do not have system temperature sensor and slow down system pump. I prefer to use delta t pump on system side as well and set to the same delta t as boiler pump.